Nanoelectrochemistry and nanophysics at electrochemical interfaces

Electrochemical interfaces provide fundamental advantages for the preparation of low-dimensional structures on metal and semiconducting substrates without irreversible modifications induced by the preparation process. Delocalized, and in particular localized electrodeposition using a scanning probe microscope tip as a nanoelectrode, allow a solely electrochemical bottom-up growth of nanostructures under defined nucleation and growth conditions. Localized electrodeposition can be utilized to grow nanoscale structures with lateral sizes of a few nanometers at defined sites both on single-crystal metal surfaces as well as on well defined hydrogen terminated n-Si(1 1 1):H surfaces. In addition, scanning probe microscopy at electrochemical interfaces allows the application of locally resolved in situ investigation techniques like tunneling and contact spectroscopy. Sophisticated in situ tunneling spectroscopy reveals important details of the molecular structure of the solid/liquid interface, and allows for probing electronic states in situ in a bias voltage interval as large as the stability range of the electrolyte, which is approximately 1 V in the case of aqueous solutions. In situ contact spectroscopy, based on the defined formation of quantized contacts between a scanning probe tip and a nanostructure underneath the tip, can be utilized for the investigation of the electronic structure of, e.g., metal/silicon interfaces, which is shown at the example of nanoscale Au diodes on n-Si(1 1 1). Thus, the combination of both, growth and in situ investigation of nanostructures at electrochemical interfaces under defined conditions opens up a fascinating perspective in view of a future nanotechnology utilizing solid/liquid interfaces.